The present invention relates to a cryptographic communication system and a cryptographic communication method and, particularly, to a cryptographic communication system and a cryptographic communication method that enhance security.
In a communication system, communication data is encrypted to prevent wiretapping, falsification and the like of the communication data. One of techniques for the encryption is common key cryptosystem in which both ends of communication use a common encryption key (which is referred to hereinafter as a common key). In the common key cryptosystem, it is necessary for both ends of communication to share the common key without a third party knowing. One of techniques to achieve that is public key cryptosystem using RSA (registered trademark), elliptic curve cryptography and the like.
A technique to provide an integrated circuit that can prevent use of an illegally copied IC is disclosed in Japanese Unexamined Patent Application Publication No. 2010-226603. A technique to generate a security word such as RSA public key or secret key using a circuit for generating unique data that is physically uncopyable or another element to thereby ensure security of an integrated circuit used in electronic equipment is disclosed in Japanese Unexamined Patent Application Publication (Translation of PCT Application) No. 2010-527219.
Further, a technique to reduce time for key exchange in a communication system to perform cryptographic communication using a common encryption key through a local area network is disclosed in Japanese Unexamined Patent Application Publication No. 2005-341528. A technique to easily verify completeness of data in data transmission/reception by ad-hoc wireless connection is disclosed in Japanese Unexamined Patent Application Publication No. 2002-26899.